Prof. RNDr. Ilona Hromadnikova, PhD.Prof. RNDr. Ilona Hromadnikova, PhD.

Department of Molecular Biology and Cell Department of Molecular Biology and Cell Pathology, Third Faculty of Medicine, Pathology, Third Faculty of Medicine,

PraguePrague

From the 10th week Pregnancies at risk

of X-linked diseases Congenital adrenal

hyperplasia (from the 6th week, because of therapy)

X chromosome – about 500 genes E.g.: haemophilia A: X-linked gene for

coagulation factor VIII Normal allele: XH

Mutant allele: Xh

Genotype PhenotypeMen XH Y unaffected

Xh Y affected

Women XH/XH homozygote, unaffected XH/Xh heterozygote Xh/Xh homozygote, affected

X-linked mutation is phenotypically expressed In all men In all homozygous women Heterozygous women – almost unaffected,

however depends on asymmetric inactivation of chromosome X

Affected man x Unaffected woman Xh/Y x XH/XH

all daugters carriers, sons unaffected

Unaffected man x carrier woman XH/Y x XH/Xh

25% unaffected son, 25% unaffected daughter, 25% carrier daughter, 25% affected son

Haemophilia type A Mutation in F8C gene – coagulation factor VIII

deficiency Incidence 1/5 000 – 10 000 newborns ♂

Haemophilia type B Mutation in F9 gene – coagulation factor IX

deficiency Incidence 1/100 000 newborns. ♂

Variable phenotype of hemorrhage into joints and muscles, easy bruising, and prolonged bleeding from wounds

http://www.pathguy.com/

Hereditary character of the disorder is known from the 19th century, occurence in Queen Victoria´s family (Victoria was a carrier)

Duchenne muscular dystrophy Incidence 1/3300 newborns ♂ DMD gene mutation -

deletions in dystrophin gene (50-70%)

Men: rapid progression of muscle degeneration and weakness (till 3-5 years), 1/3 mental retardation, usually respirational or heart failure by age 20

Women: depends on the inactivation of chromosome X ratio, often no manifestation, cardiac abnormality Gowers' sign

Becker muscular dystrophy Milder symptoms BMD – if patients are able to walk at the age of 16 Incidence 3-6/100 000 newborns ♂ Mutation in DMD gene, mutant alleles –

production of dystrophin– change or lower production

Mucopolysaccharidosis type II. (Hunter syndrome) Incidence 1/70 000 Iduronate sulfatase deficiency →

tissue deposits of mucopolysaccharides (DM) and urinary excretion of large amounts of chondroitin sulfate B and heparitin sulfate → dysostosis with dwarfism, grotesque facies, hepatosplenomegaly, cardiovascular disorders

http://www.hunterpatients.com

Bruton agammaglobulinemia Primary immunodeficiency, incidence 1/150 000 Mutations in BTK gene, failure to produce mature

B lymphocytes and failure of Ig heavy chain rearrangement → no mature B lymphocytes, no Igs,

Sensitivity to infections

Lymphoproliferative syndrome (XLP1, Duncan syndrome)

Frequency <1/100 000 Mutation of cytoplasmic adaptor protein SAP (T and

NK cells) – associated with adhesion and activation receptors (CD150, CD244, CD229), inhibits their activity

Usually no manifestation until EBV exposure EBV fatal infections - infectious mononucleosis,

hypogammaglobulinemia, lymphoma or other lymfoproliferative disease

Wiskott-Aldrich syndrome (combined humoral and cell immunodeficiency)

Frequency <1/100 000 Mutation in WASP gene – cytoplasmic protein in

haematopoiesis , signal transduction to cytoskeleton → abnormalities in migration and phagocytosis, activation of T and B lymphocytes

↓thrombocytes, ↓ T lymf., ↓ IgM, ↑ IgA, IgE and IgD, eczema, sensitivity to pyogenic bacteria, autoimmunity symptoms – hemolytic anaemia, vasculitis, polyarthritis, non-specific intestinal inflammation

Granulomatous disease (defect in phagocytosis) Incidence <1/100 000 Mutations in genes coding NADPH oxidase system:

reaction of NADPH with oxygen → reactive oxygen species (ROS), “respiratory burst“ – antimicrobial effect) → inability of phagocytes to kill microbes that they have ingested

Skin abscesses, granulomas, recurrent infections of epithelial surfaces

Most dangerous - bacteria with catalase production (digests H2O2 – in low level always producted) – Staphylococcus, Salmonella

Fungal infections (Aspergillus fumigatus, Candida)

SCID-X1: Severe combined immunodeficiency, X-linked

Almost ½ of SCIDs Mutation in the gene encoding

the subnunit γ (CD 132) of IL-2, IL-4, IL-7, IL-9, IL-15, IL-21 receptor → defect in cytokine signal pathways

Nonfunctional B and T lymphocytes system – 0 T and NK cells, B lymphocytes present – no Abs production

Receptorová rodina – společná signalizační podjednotka

Hořejší, Bartůňková (2001)

Hypohidrotic ectodermal dysplasia Incidence 1/100 000 Mutated EDA gene – ectodysplasin-A,

signal cascade protein, critical for interaction of ectoderm and mesoderm during embryogenesis

Hypotrichosis: sparse (limited) scalp and body hair hypohidrosis: reduced ability to sweathypodontia: absent or malformed teethhyperthermia

Barth syndrome (cardioskeletal myopathy) Incidence <1/100 000 Mutated BTHS gene for tafazzin (TAZ,

acyltransferase), important for cardiolipin biosynthesis in mitochondria) Cardiolipin –inner mitochondrial membrane, necessary for

proper function of the electron transport chain, heart and muscle tissue

Cardiomyopathy, neutropenia, skeletal myopathy, and abnormal mitochondria (low AGP production)

Often death of infants (cardial failure, sepsis during agranulocytosis)

Hydrocephalus, X-linked (most common inherited) Incidence <1/100 000 Mutation in the gene encoding the L1 cell adhesion

molecule, mainly in nervous system Enlarged cerebral ventricles and mental retardation,

often with spastic paraparesis (partial loss of movements)

Rett syndrome Mutation in the gene encoding methyl-CpG-

binding protein-2 (important for chromosome X inactivation)

Neurodevelopmental disorder that occurs almost exclusively in females, for males lethal in utero

Arrested development between 6 and 18 months of age, regression of acquired skills, loss of speech, stereotypical movements (classically of the hands), microcephaly, seizures, and mental retardation, epilepsy (about 75% of cases)

Congenital adrenal hyperplasia Deficiency in one or more enzymes important for

cortisol biosynthesis 95% of cases - 21-hydroxylase → overproduction

and accumulation of cortisol precursors → excessive production of androgens

In female newborns virilization: the external genitalia are masculinized; gonads and internal genitalia are normal

25% - simple virilizing, 75% salt-wasting form Dexamethasone – prevents genital masculinization

in female fetuses, application necessary from the 5. – 9. week of gestation

Amplification of paternally inherited alleles using real-time PCR

SRY gene (sex determining region) -1 copyDYS 14 gene (TSPY1- testis specific protein) – variable number of copies

From the 10th week using SRY gene -100% sensitivity and 100% specificity

From the 6th week using SRY gene – risk of false negative results

SRY encodes transcription factor - testis-determining factor (TDF)

 member of the high mobility group (HMG)-box family of DNA-binding proteins that contain a zinc finger domain

initiates male sex determination Mutations give rise to XY females

with gonadal dysgenesis (Swyer syndrome)

translocation of part of the Y chromosome containing SRY gene to the X chromosome causes XX male syndrome

Development of testis Spermatogonia Protective Sertoli cells (maturation

of sperms) Leydig cells, production of

testosterone

http://anatomy.iupui.edu

Pseudogene of pJA923 gene, encodes TSPY (testis-specific protein, Y encoded)

Inter-individual variations 50 – 200 copies/Y chr. TSPY expression in spermatogonia,

spermatocytes, unknown function Aberant expression of TSPY in the cases of

carcinoma of testis or prostate

X–linked diseases – female foetuses are carriers, CVS and/or AMC is not necessary, later confirmation by ultrasound

Indication to non-invasive examination from the 10th-12th week of gestation or when needed

Male foetuses– 50% risk of mutant allele presence, 50% risk of disease – indication to CVS or AMC for confirmation or exclusion of mutant allele

CAH – dexamethasone treatment, as early as possible – prevents malformation of the female genitals

Non-invasive examination from the 6th week of gestation

CAH – male foetuses, possibility to terminate therapy (dexamethasone)

Non-invasive fetal sex determination

SAFE (Special Non-Invasive Advances in Foetal and Neonatal Evaluation Network)

project , 6.RP, Network of Excellence,